In a long-term evolution (LTE) system, methods for controlling power in transmitting a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), an uplink sounding reference signal (SRS) and a physical random access channel (PRACH) by a UE are defined. When the UE is configured with multiple carriers, independent power control of uplink transmission signal is performed in each serving cell;
when the PUSCH and the PUCCH cannot be transmitted at the same time, a power control formula of the PUSCH is:
                                                        P                              PUSCH                ,                c                                      ⁡                          (              i              )                                =                                          ⁢                      min            ⁢                                          {                                                                                                                                                          P                                                          CMAX                              ,                              c                                                                                ⁡                                                      (                            i                            )                                                                          ,                                                                                                                                                                                                                                                                    10                                ⁢                                                                                                      log                                    10                                                                    ⁡                                                                      (                                                                                                                  M                                                                                  PUSCH                                          ,                                          c                                                                                                                    ⁡                                                                              (                                        i                                        )                                                                                                              )                                                                                                                              +                                                                                                P                                                                                                            O                                      ⁢                                      _                                      ⁢                                      PUSCH                                                                        ,                                    c                                                                                                  ⁡                                                                  (                                  j                                  )                                                                                            +                                                                                                                                                                                                                                                                                                α                                    c                                                                    ⁡                                                                      (                                    j                                    )                                                                                                  ·                                                                  PL                                  c                                                                                            +                                                                                                Δ                                                                      TF                                    ,                                    c                                                                                                  ⁡                                                                  (                                  i                                  )                                                                                            +                                                                                                f                                  c                                                                ⁡                                                                  (                                  i                                  )                                                                                                                                                                                                                                        }                            ⁢                                                          [              dBm              ]                                      ;                            (        1        )            
and when the PUSCH and the PUCCH can be transmitted at the same time, the power control formula of the PUSCH is:
                                                        P                              PUSCH                ,                c                                      ⁡                          (              i              )                                =                                          ⁢                      min            ⁢                                          {                                                                                                                              10                          ⁢                                                                                    log                              10                                                        ⁡                                                          (                                                                                                                                                                          P                                      ^                                                                                                              CMAX                                      ,                                      c                                                                                                        ⁡                                                                      (                                    i                                    )                                                                                                  -                                                                                                                                            P                                      ^                                                                        PUSCCH                                                                    ⁡                                                                      (                                    i                                    )                                                                                                                              )                                                                                                      ,                                                                                                                                                                                                                                                                    10                                ⁢                                                                                                      log                                    10                                                                    ⁡                                                                      (                                                                                                                  M                                                                                  PUSCH                                          ,                                          c                                                                                                                    ⁡                                                                              (                                        i                                        )                                                                                                              )                                                                                                                              +                                                                                                P                                                                                                            O                                      ⁢                                      _                                      ⁢                                      PUSCH                                                                        ,                                    c                                                                                                  ⁡                                                                  (                                  j                                  )                                                                                            +                                                                                                                                                                                                                                                                                                α                                    c                                                                    ⁡                                                                      (                                    j                                    )                                                                                                  ·                                                                  PL                                  c                                                                                            +                                                                                                Δ                                                                      TF                                    ,                                    c                                                                                                  ⁡                                                                  (                                  i                                  )                                                                                            +                                                                                                f                                  c                                                                ⁡                                                                  (                                  i                                  )                                                                                                                                                                                                                                        }                            ⁢                                                          [              dBm              ]                                      ;                            (        2        )            
and a power control formula of the PUCCH is:
                                          P            PUCCH                    ⁡                      (            i            )                          =                                  ⁢                  min          ⁢                                                    {                                                                                                                                                          P                                                          CMAX                              ,                              c                                                                                ⁡                                                      (                            i                            )                                                                          ,                                                                                                                                                                                                                                                                    P                                                                  0                                  ⁢                                                                      _                                    ⁢                                    PUCCH                                                                                                                              +                                                              PL                                c                                                            +                                                              h                                ⁡                                                                  (                                                                                                            n                                      CQI                                                                        ,                                                                          n                                      HARQ                                                                        ,                                                                          n                                      SR                                                                                                        )                                                                                            +                                                                                                                                                                                                                                                            Δ                                                                                                            F                                      ⁢                                      _                                      ⁢                                      PUCCH                                                                        ,                                    c                                                                                                  ⁡                                                                  (                                  F                                  )                                                                                            +                                                                                                Δ                                  TxD                                                                ⁡                                                                  (                                                                      F                                    ′                                                                    )                                                                                            +                                                              g                                ⁡                                                                  (                                  i                                  )                                                                                                                                                                                                                                        }                            ⁢                                                          [              dBm              ]                        .                                              (        3        )            
In the LTE system, if the UE is configured to be unable to transmit the PUSCH and the PUCCH at the same time, the same UE will not transmit the PUSCH and the PUCCH in the same one or more carriers in the same subframe at the same time. And when the UE is configured to be able to transmit the PUSCH and the PUCCH at the same time, the same UE may transmit the PUSCH and the PUCCH in the same one or more carriers in the same subframe at the same time. However, the PUCCH is only transmitted in a primary component carrier (PCC). Uplink control information (UCI) carried by the PUSCH contains UCI of all corresponding carriers, and the uplink information can only be transmitted in a PUSCH in a carrier. That is, the UCI of all the corresponding carriers is either combined, or partially dropped according to a predetermined criterion, and is finally transmitted via a PUCCH and/or a PUSCH in a CC only.
When transmission power of the uplink signal exceeds configured maximum output power (PCMAX) of the UE, that is, outflow of the output power of the UE occurs, transmission power used by the UE in transmitting the above uplink signal will be equal to the PCMAX of the UE. And the UE will adjust power of a corresponding uplink channel.
FIG. 1 is a schematic diagram of simultaneously transmitting multiple PUCCHs by a UE in an LTE-A system at different cells in the same subframe, FIG. 2 is a schematic diagram of simultaneously transmitting multiple PUSCHs by a UE in an LTE-A system at different cells in the same subframe, FIG. 3 is a schematic diagram of simultaneously transmitting PUCCHs and PUSCHs by a UE in an LTE-A system at different cells in the same subframe, and FIG. 4 is a schematic diagram of simultaneously transmitting PUCCHs and PUSCHs by a UE in an LTE-A system at a primary serving cell in the same subframe.
As shown in FIG. 1, as a carrier aggregation technique is used, when the UE is configured with multiple serving cells, simultaneous transmission of multiple PUCCHs at different serving cells in the same subframe will occur; or as shown in FIG. 2, multiple PUSCHs are simultaneously transmitted at different serving cells; or, as shown in FIG. 3, the PUCCHs and PUSCHs are simultaneously transmitted. And on the other hand, as abilities of the UE are enhanced, as shown in FIG. 4, the UE may simultaneously transmit the PUCCHs and PUSCHs at the primary serving cell in the same subframe.
When the above case occurs, that is, the UE needs to simultaneously transmit multiple PUSCHs in the same subframe, or the UE needs to simultaneously transmit PUSCHs and PUCCHs, it will occur that a total sum of transmission power of multiple PUSCHs is greater than the PCMAX of the UE, or a total sum of transmission power of PUSCHs and PUCCHs is greater than the PCMAX of the UE. In order to direct transmission power allocation of the UE in such a case, a power control method in a case where transmission power of a UE is limited is defined in LTE-A standardization, which is as follows:
when only multiple PUSCHs with no UCI need to be simultaneously transmitted, if total transmission power obtained at this moment exceeds the PCMAX of the UE, the UE lowers the transmission power by equal share in each PUSCH, until it is ensured that the total transmission power is less than or equal to the PCMAX of the UE;
when PUSCHs with no UCI and PUCCHs need to be simultaneously transmitted, if total transmission power obtained at this moment exceeds the PCMAX of the UE, the UE first ensures that the transmission power of the PUCCHs is satisfied, and then lowers the transmission power by equal share in each PUSCH with no UCI, until it is ensured that the total transmission power is less than or equal to the PCMAX of the UE, as shown in formula (4);
for example, when the PUSCHs with no UCI and PUCCHs are simultaneously transmitted, the transmission power of the PUCCHs is preferentially ensured:
                                                        ∑              c                        ⁢                                          w                ⁡                                  (                  i                  )                                            ·                                                                    P                    ^                                                        PUSCH                    ,                    c                                                  ⁡                                  (                  i                  )                                                              ≤                      (                                                                                P                    ^                                    CMAX                                ⁡                                  (                  i                  )                                            -                                                                    P                    ^                                    PUCCH                                ⁡                                  (                  i                  )                                                      )                          ;                            (        4        )            
when PUSCHs with no UCI and PUSCHs with UCI need to be simultaneously transmitted, if total transmission power obtained at this moment exceeds the PCMAX of the UE, the UE first ensures that the transmission power of the PUSCHs with UCI is satisfied, and then lowers the transmission power by equal share in each PUSCH with no UCI, until it is ensured that the total transmission power is less than or equal to the PCMAX of the UE, as shown in formula (5);
for example, when the PUSCHs with no UCI and PUSCHs with UCI are simultaneously transmitted, the transmission power of the PUSCHs with UCI is preferentially ensured:
                                                        ∑                              c                ≠                j                                      ⁢                                          w                ⁡                                  (                  i                  )                                            ·                                                                    P                    ^                                                        PUSCH                    ,                    c                                                  ⁡                                  (                  i                  )                                                              ≤                      (                                                                                P                    ^                                    CMAX                                ⁡                                  (                  i                  )                                            -                                                                    P                    ^                                                        PUSCH                    ,                    j                                                  ⁡                                  (                  i                  )                                                      )                          ;                            (        5        )            
when PUCCHs, PUSCHs with no UCI and PUSCHs with UCI need to be simultaneously transmitted, if total transmission power obtained at this moment exceeds the PCMAX of the UE, the UE first ensures that the transmission power of the PUCCHs is satisfied, then the transmission power of the PUSCHs with UCI is satisfied, and thereafter lowers the transmission power by equal share in each PUSCH with no UCI, until it is ensured that the total transmission power is less than or equal to the PCMAX of the UE, as shown in formula (6);
for example, when the PUCCHs, PUSCHs with UCI and PUSCHs with no UCI are simultaneously transmitted, the transmission power of the PUCCHs is ensured first, then the transmission power of the PUSCHs with UCI is ensured, and thereafter the transmission power of the PUSCHs with no UCI is ensured:
                                                                        P                ^                                            PUSCH                ,                j                                      ⁡                          (              i              )                                =                      min            ⁡                          (                                                                                          P                      ^                                                              PUSCH                      ,                      j                                                        ⁡                                      (                    i                    )                                                  ,                                  (                                                                                                              P                          ^                                                CMAX                                            ⁡                                              (                        i                        )                                                              -                                                                                            P                          ^                                                PUCCH                                            ⁡                                              (                        i                        )                                                                              )                                            )                                      ,                                  ⁢                                            ∑                              c                ≠                j                                      ⁢                                          w                ⁡                                  (                  i                  )                                            ·                                                                    P                    ^                                                        PUSCH                    ,                    c                                                  ⁡                                  (                  i                  )                                                              ≤                                    (                                                                                          P                      ^                                        CMAX                                    ⁡                                      (                    i                    )                                                  -                                                                            P                      ^                                        PUCCH                                    ⁡                                      (                    i                    )                                                  -                                                                            P                      ^                                                              PUSCH                      ,                      j                                                        ⁡                                      (                    i                    )                                                              )                        .                                              (        6        )            
Power control of an uplink channel for a serving cell, or power control of transmitting an uplink channel by a primary serving cell and a secondary serving cell under a multicarrier technology, is only defined in the current standards.
However, as continuous development of small base stations, there will occur a scenario in Rel. 12 where there exist multiple small base stations under coverage of a macro base station (such as an eNB). Coverage of the small base stations is relatively small, and the number of them is relatively large. The small base stations may occupy frequency points different from or identical to those occupied by the macro base station. Backhauls between the small base stations and the macro base station may be ideal, that is, latency is very small or may be completely neglectable, and a transmission ability is powerful. And more typically, the backhauls are non-ideal, that is, transmission latency is relatively large and the transmission ability is limited. The power control of the uplink channel of the UE in such scenarios are not taken into account in the current standards.
It should be noted that the above description of the background is merely provided for clear and complete explanation of the present disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of the present disclosure.